Many different resealable containers have been described in the literature. An important demand placed on these is that it must be easy to see whether the container has been opened. This is particularly important for resealable foodstuff containers, since an open container always yields reduced tightness and, thus, the risk of foreign microorganisms and the like entering the container.
Also for containers containing wet products, e.g. wipes, there is a need of visible proof that a container has been opened, since the liquid inside an open package evaporates more easily. In these containers, there may also be problems with undesired microorganisms if the container is intended for e.g. sterile compresses or the like.
U.S. Pat. No. 4,679,693 discloses a resealable container comprising a casing and a label having a pulling tab defined by two parallel perforated lines and intended for opening the container, a removed pulling tab indicating that the container has been opened. To secure the container against opening of the label from any other position than the one in which the pulling tab is located, either permanent adhesive or slits are arranged in the periphery of the label, such slits tearing if one tries to open the container. Inside the permanently attached periphery or inside the slits, there is a perforated line which defines an opening tab in the label.
EP-A1-0,249,337 discloses a resealable container having a releasably attached covering foil which has a pulling tab for opening the container. Also in this case, a removed pulling tab indicates that the container has been opened. To protect the container from being opened from a position other than the one in which the pulling tab is located, inclined cuts have been formed in the periphery of the covering foil. This causes the forming of small triangular portions in the periphery of the covering foil if one tries to open the container from these directions, which clearly proves that someone has opened or tampered with the container adjacent these cuts.
In many cases, the surface on which the label or covering foil is to be applied can be limited. Consequently, it can be difficult to accommodate the additional space required for a pulling tab. Moreover, it should be possible to uncover a sufficiently large opening in the container to reach the packed product, which entails that outside the opening of the container there is only a restricted surface on which the label or covering foil can be releasably attached. A drawback of the technique described above is that pulling tabs and cuts require too large a space on the casing.